Isocyanate dimers as color forming intermediates



Patented June 23, 1953 OFFICE ISOCYANATE DIMERS AS COLOR FORMING INTERMEDIATES I Otto Stallmann, Bridgeton, N. J., and Esley 0. Langerak, Wilmington, Del., assignors to E. I. duPont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application November 16, 1951,

Serial No. 256,819

3 Claims. (01. 260-239) This invention relates to the preparation of stable isocyanate derivativesof dyes and colorformin-g intermediates useful in the preparation of dyes. The invention relates more particularly to new dyes and color-forming intermediates which contain an aromatic isocyanate dimer nucleus which when applied to textiles, paper, leather, etc., exhibit improved fastness to washing.

It is recognized in the field of dyes, particularly for cotton and other cellulose fibers, that many of the compounds which dye these materials in light-fast shades are frequently deficient in their fastness to washing. This problem exists particularly in the field of direct dyes which are used in dyeing cellulose material, and in many of the developed dyes particularly of the azo class. As will be illustrated, the invention is not limited to dyes which find their primary use in the dyeing of cellulose materials but is also applicable to the preparation of colors and color intermediates with improved wet fastness which may also be used in the coloring of paper, leather and the nitrogenous-containing fibers such as wool, silk, nylon, etc., or, in other words, for use in the coloring of any material with which isocyanate groups react to effect a chemical bond.

It is therefore an object of the present invention to produce dyes and dye intermediates containing isocyanate dimer linkages which exhibit improved wash fastness when applied to textiles, paper, leather and other materials with which isocyanate groups react.

The compounds of the present invention have the following general formula:

Aryl stands for the nucleus of an aromatic coma pound capable of being converted to an isocyanate which in turn can be dimerized either with itself or with another aryl isocyanate to form a stable dimer which can be broken down with heat, as hereinafter described.

While in the literature it has generally been assumed that the dimerization of aromatic isocyanates produces uretidine-dione rings of the formula:

of two aromatic isocyanate molecules gives the 1,3-oxazetidine ring of the formula:

The invention of the present application is not-based on a particularly theoretical molecular arrangement but on the known fact that the isocyanates, when polymerized to a dimer, irrespective of the chemical formula that may be assigned thereto, are rendered relatively inactive so that compounds containing them can be subjected to various chemical reactions without destroying the potential value of the isocyanate groups, yet on heating the dimer is split, resulting in the liberation of free isocyanate groups which can then react with materials containing reactive hydrogen or other compounds with which it is known that compounds containing free isocyanate groups will react.

In general, the aryl isocyanates may be prepared either from the aromatic nitroamines or aromatic nitrocarboxylic acids which are converted to isocyanate compounds by known reac-- tions. These aromatic monoisocyanates may then be converted to stable dimers by a dimerization reaction using pyridine as the catalyst, or by using mixed aromatic phosphines as more particularly described in co-pending application Serial No. 248,270.

Where the aryl compounds carry amino groups they are diazotized and then coupled with any of the usual azo coupling components to form dyes which, after application and drying on the material to be colored, are fixed thereto by a heating operation which splits the isocyanate dimer and. permits the isocyanate group to attach itself to reactive groups such as through reactive hydrogen in the materials which are to be dyed.

The stable isocyanate dimer intermediates or dyes, as hereinafter illustrated, make it possible to obtain wash-fast colors with dyes heretofore possessing poor or mediocre washfastness. It is believed that this is due to direct chemical reaction between the reactive hydrogen atoms in the textile and the free -NCO groups formed when the dimeric isocyanate group of the stable '4 The dried product melts at from 209 to 211 C. and has the following probable formula:

of result. This rupturing is brought about by heat 140 parts of benzene 1s catalytlcally reduced with ing the textile, paper or leather, etc., on which 5 parts of a 3% palladlum'on'charcoal fatalyst the stable intermediate has been deposited, to finder g fl s i g temperatures of from 120 to 200 C. for varying fi from o 31 b j ys i lengths of time, longer times being required for 0 p are remov.ed filtratlon e car on lower temperatures. Preferably, from 3 to '10 Cake eiitracted Wlth 160 parts and minutes at from 0 to is used the combined acetone-benzene SO1lltl0l'l lS evapo- The compounds may be used in different ways rated to dryness h product obtamed 1s according to the wish of the operator. Thus, on 15 graypowder q melt sharply the one hand, the stable intermediate may be It 15 m Soluble m mute aclds i m formed to include the entire dye molecule and tetrazotized at 0 C. by the usual d1azot1zat1on U processes. g g g g ggg gi ig g zg ggg 'g i fiz g ifi The structure of the product is believed to be: is dried at from 100 to 105 C. in a conventional H NH manner such as in a continuous drying oven. After drying, the fabric is baked, again in a con- Example 2 a ventional type of curing oven. Normally this will be carried out in a continuous manner, the dried 1'amIPOA'mtrOnaPhthaIQnB 1s converted to cloth passing in one end of the oven and passing the l'mtro'4'naphFha'lene lsocyanate by means over rolls in the oven for a fixed time and then of phosgene employmg wen one emerging as the baked or cured fabric with the h.undr.ed (.100) parts of sand lsocyanate are dye chemically bound to the texma dimerized in 2000 parts of alpha-methyl;naph- On the other hand, the stable intermediate may thalene whlle standmg for hours at 35 m have reactive groups such as amino groups which presence 9 part of ,hmethyl R l are further reacted or coupled to other intermephme' The lsqcyanate mm?! obtamed 15 diates to form the dye. In this case the dimermoved by mutation Washed Wlth 50.133115 of containing intermediate may be anchored to the 28118 thenc Wlth p tetrachlonde and t textile first by heat treatment and then the dye at from 50 to Ten.(10) parts of the dlmer molecule may be formed on free reactive porprepared 1s,cata1yt1any reduced by tion. If the free portion is an NI-I2 group, it lowmg reductlon P q of Example. 1 i may be diazotized and then coupled in the same the ammo compound is isolated as described in manner as is used in the so-called ice colors. that example In some cases it is desirable to remove water end product 15 beheved to have the from the fabric completely before the dyeing 40 lowmg formula:- operation or after, after which the heating to break the dimer ring and cause reaction with the fiber is carried out. It is believed that the HzN NH, freed -NCO groups react with the OI-I groups of the cellulose more readily in the absence of water. On the other hand, this is not so impor- Example 3 tant when the material to which the -NCO (a) parts of the diammophenyl dimer v group is to react contains groups, f the pared as in Example 1 is dissolved in 7.1 parts of appears to react with them more readily 10 Normal hydrochloric acid and 100 parts of than with Water water added. It is cooled to 0i1 C. and 6.6 The following exammes are given to illustrate parts of 5 Normal sodium nitrite solution is added the invention. The parts used are by Weight and the solution is stirred for 30 minutes. The In these examples, D refers to the isocyanate excess sodium nitrite is destroyed by adding a 1 dimer nucleus, as identifi d above molar solution of sulfamic acid slowly until a Z 1 blue color on starch-iodide indicator paper is Exam 8 no longer obtained. The solution is clarified by One hundred (100) parts of p-nitrophenylisoadding approximately 1 part of activated carcyanate, prepared by the well-known reaction bon, stirring and filtering. of phosgene on p-nitroaniline, is dissolved in (b) 55 parts of this diazo solution is then add- 1100 parts of dry nitrobenzene. Three to five ed slowly to a solution of 3.54 parts of l-phenyldrops of dimethylphenylphosphine are added, 3-methyl pyrazolone-5 in 100 parts of water and and after standing four hours at room tempera- 5.6 parts of 10 Normal sodium hydroxide and 5.5 ture the solid mass of pale yellow crystals which parts of 2 Normal sodium carbonate. A red prehas formed is removed by filtration, washed well cipitate is formed rapidly. It is filtered oil, with petroleum ether, carbontetrachloride or washed with water and dried. The product has acetone, and dried. at temperatures up to C. the following structural formula:

H3c- ?N=N On-C -N=N d-o-cm (a) A piece of cotton broadcloth weighing parts is soaked in water for about 15 minutes. It is then wrung out and soaked in acetone for about 15 minutes. It is wrung out again and then soaked 15 minutes in pyridine. This effectively removes water from the fiber and leaves it in a swollen condition. v v

1.5 parts of the dye prepared above is dissolved in 150 parts of dimethyl formamide, the fabric still wet with pyridine is added, and heated at reflux for two hours. The fabric is removed, rinsed with acetone and then with water and soaped lightly to remove surface dye. The fabric is dyed a yellow color.

Example 3 (b)] and the dye is isolated. The dye has the following structure:

Cotton broadcloth was dyed with the dye in the same manner as in Example 3 (0) except that It is believed that the dimer portion of the o-dichlorobenzene is used as the solvent in place molecule is ruptured and the freed NCO groups react with the OH groups of the cotton to give a urethane linkage as follows:

of dimethyl formamide. Prolonged extraction with dimethyl formamide which normally would extract all of the dye, showed about 50% color retention on the fabric due to chemically bonding H through the is-ooyanate linkages. The cloth was cellulose-0-CIl&T ON=NfiJ-?-CHa dyed a brown color.

Example 5 (d) When the dyed fabric is washed with a 0.5% sodium oleate soap solution at 100 C. for one hour there is no loss of color. This same dye without the anchoring urethane linkage is practically all removed from the cloth in a similar wash.

(e) Another sample of the dyeing is extracted for one hour in boiling dimethyl formamide. An 80%85% retention of color on the fiber is observed. An unanchored dye is essentially completely removed by this stripping operation.

(1) Another sample of the dyeing was discharged with alkaline sodium hydrosulfite to a colorless fabric. The fabric was rediazotized and coupled with l-phenyl-3-methyl pyrazolone-5 and the original color was redeveloped in essentially full strength.

Example 4 The diazotized amine of Example 3 (a) is coupled to beta-naphthol in the conventional way NaOIS exhaustion, an orange-yellow color is obtained.

The fabric is then rinsed with acetone to replace the water. One-half of the fabric is then heated in pyridine at the reflux for two hours to split the dimer ring and attach the dye to the fabric. The

treated fabric is compared to the untreated fabric for retention of dye on boiling with 5% soap solution for one hour. Considerably more dye is retained on the fabric in the case of the pyridine treated fabric.

When the sodium salt of benzoyl J -acid is substituted for the l-(m-sulfophenyl) -3-methyl pyrazolone-5 a purple dye is obtained with essentially the same fastness properties.

The dye has the formula:

E'aiample 6 The diazotized amine of Example 3 (a) is coupled with R-salt to give a dye with the structure:

NaOiS SOaNa This compound dyed cotton a red color, with a bluish shade. 110,

As further illustrative of the aminoisocyanate dimers which may be used as tetrazo components according to this invention can be mentioned 5 the following:

HzN-QDQ-NH:

in which R is alkyl, alkoxy, halogen, -CO-alkyl, -CO-ary1, COO-alkyl, etc., in which the alkyl and aryl radicals contain up to '7 carbon atoms, for example:

HzN- 1) NH:

I OH;

HsC

Cl Cl 1 e 20 C I I HnN NH:

and those in which the amino group is an aryl radical more remote from the dimer, such as:

a mo

OCH: 25

NH: NH:

Also, in a similar manner any of the azo dye cou- 5O pling components may be substituted for those used in the specific examples. As further illustrative of this class may be mentioned those having the formula:

I CH

It is of course understood that the present invention is not limited to the specific examples or the alternatives listed above but may be applied in the manner clearly illustrated to any compounds the azo component of which is capable of being converted to an isocyanate which carries groups that may be diazotized or serve as intermediates for the preparation of diazo compounds, and that the coupling components may be of any type desired for the preparation of dyes.

While the formulae given in the specific examples of how the dye is chemically linked to the cellulose or other material to be dyed is believed 10 to be a logical explanation of the attachment of these new isocyanate compounds to the fibers or other substrate, it is of course understood that the invention is not limited by any theory or of the following general formula:

in which Aryl-D-Aryl stands for a dimer of aryl isocyanates of the benzene and naphthalene series.

2. The compound of the general formula:

in which D stands for an isocyanate dimer linkage between the two phenyl nuclei.

3. The compound of the general formula:

in which D stands for an isocyanate dimer linkage between the two phenyl nuclei.

OTTO STALLMANN. ESLEY O. LANGERAK.

No references cited. 

1. THE COMPOUNDS OF THE FOLLOWING GENERAL FORMULA: 